The biggest known star in the cosmos is in its death throes and will eventually explode, astronomers said on Wednesday. Using a telescope at the European Southern Observatory in Chile, the astronomers said they had spotted telltale signs in a star called W26 Located about 16,000 light years away in the constellation of Ara, or The Altar, the star has a diameter 3,000 times that of the Sun. W26, first observed in 1998, is a "red supergiant", a term for a star that is as big as it is short-lived. Stars of this kind typically have lifetimes of less than a few million years before they exhaust their nuclear fuel and explode as supernovae. W26 is becoming unstable and shedding its outer layers, a key step in the death process, according to the paper, published in the British journal Monthly Notices of Britain's Royal Astronomical Society (RAS). W26 is "the largest known star in the Universe", the RAS said in a press release.